1. Field of the Invention
The present invention relates to digital switching systems, such as voice and data switches, in general, and in particular to those systems employing plural processors for control in a distributed switching environment. More particularly still, it relates to a quasi-independent system and method within the digital switch for surveillance, messaging and limited control of the distributed plural system units.
2. General Prior Art of the Invention
The general prior art digital time division switching system exhibits a hierarchical, two-plane organization comprising duplicate central controllers (CC) at the top, followed by central message controllers (CMC) then by the network modules (NM) proper as well as input-output controllers (IOC). This general architecture is also that within which the system and method of the present invention operate. Such prior art system is disclosed in U.S. Pat. No. 4,213,201 granted Jul. 15, 1980 to Gagnier et al, which is incorporated herein by reference.
A useful general overview of this category of switching systems is given in an article by Robert Wood entitled "DMS-100 technology evolution", at page 6 in Telesis, Volume 10, Number 3, 1983.